Efficacy of Bacteriophage Against Multidrug Resistant Staphylococcus spp. Isolates

Background The increasing emergence of multidrug-resistant Staphylococcus spp. has become a major public health concern worldwide. Bacteriophages are being considered as potential alternative antibacterial agents against resistant bacterial pathogens. This study aimed to isolate bacteriophages from cow dung samples and evaluate their lytic activity against Staphylococcus spp. isolates obtained from apparently healthy individuals. Materials and Methods A total of five Staphylococcus spp. isolates (S1–S5) were obtained from swab samples collected from different body sites of apparently healthy individuals residing in Dhaka city, Bangladesh. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method. Bacteriophages were isolated from cow dung samples through enrichment and filtration procedures. Phage lytic activity was evaluated using spot assay and Double-Layer Agar (DLA) methods. The inhibitory effect of the selected bacteriophage lysate was further assessed by turbidity observation and optical density (OD 600 ) measurements. Results All five isolates demonstrated resistance to oxacillin, while ciprofloxacin showed comparatively higher activity against most isolates. During spot assay screening, isolate S2 demonstrated visible susceptibility to all four isolated bacteriophage lysates (PS1, PS2, PS3, and PS4), whereas the remaining isolates exhibited weak or no visible lytic activity. The DLA assay confirmed plaque formation and bacterial clearing against isolate S2, with a PFU count of 2.78 × 10 8 PFU/ml obtained from the 100 μl phage inoculum plate. Higher phage concentrations demonstrated comparatively greater reduction in bacterial turbidity and OD values during the inhibition assay. Conclusion The findings of this study suggest that cow dung may serve as a potential environmental source of bacteriophages capable of showing lytic activity against selected multidrug-resistant Staphylococcus spp. isolates. However, further molecular characterization, broader host range analysis, and in vivo investigations are necessary to better evaluate their therapeutic potential.